Brush adapter for dynamoelectric machines



June 8, 1957 s. A. SILVERMAN 2,796,544

BRUSH ADAPTER FOR DYNAMOELEGTRIC MACHINES Filed July 19, 1954 ATTORNEYS Ufiitfid States Patdifo BRUSH ADAPTER FOR DYNAMOELECTRIC MACHINES This invention relates to current carrying brushes for dynamoelectric machines and particularly to an improved wear compensating adapter for such brushes.

Brushes, commonly made of compressed carbon, are employed in dynamoelectric machines for conducting current between the rotating and stationary'members; for example, brushes are employed to conduct current between the stator and rotor of direct current machines and'are held in continuous engagement with the rotating commutator. Spring pressed fingers are employed to maintain the required pressure between the brushes and the commutator, and, as the brush wears, the finger follows the brush and maintains pressure until the wear is sufficient to require replacement of the brush. 'In many applications when the brush is worn sufficiently to require replacement it still has a substantial length between the worn end and the metal connector which is suitable for use but cannot be used because of 'limited range of movement ofthe brush following mechanism or a spring finger. Inserts or adapters have been provided to make possible the further use of the brush'in such cases by restoring the eifectivelength thereof; these devices however, have not proved entirely satisfactory, and have not come into gen-' eral use. Accordingly, it is an object of this invention to provide an improved wear compensating adapter forthe brushes of dynamoelectric machines which is of simple construction, is easily installed and is reliable in operation.

It is another object of this invention to provide an improved wear compensating adapter for the brushes of dynamoelectric machines which is readily attached and removed from the brush and also facilitates handling of the adapter and brush as a unitary assembly during servicing of the machine.

Briefly, in carrying out the objects of this invention in one embodiment thereof, a brush wear adapter is provided which comprises a block having a cross section substantially the same as that of the brush so that it may move in the brush guide in the same manner as the brush. The height of the adapter block is made substantially equal to the normal maximum permissible wear of the brush. Thus, after the brush has worn its normal permissible amount the adapterrnay be inserted and will restore the spring pressure relationship of the brush following mechanism so that the brush may be used again until an equal amount of wear has occurred thereby resulting in a great saving of brush material. The adapter is provided with recesses or guide passages in alignment with the direction of brush movement and in positions to afford passage for the brush shunt or pigtail connectors. These recesses are open laterally of the block so that they may he slipped over the shunts, and further are proportioned so that they act as guides for the adapter and facilitate handling of the adapter and worn brush as a unitary assembly without likelihood of dislodging the adapter from its position on the brush. In other embodiments, the form of the wear adapter is varied for different brush applications.

Patented June 18, 1957 The features of this invention which are believed to be novel are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a side elevation view partly in section of a dynamoelectric machine brush assembly provided with a wear compensating adapter embodying this invention;

Fig. 2 is an enlarged perspective view of the upper portion of the'brush and adapter shown in Fig. 1;

Fig. 3 is a plan view of one end of the brush and adapter of Fig. 2;

Fig. 4 is a view similar to Fig. 2 showing a modified form of the invention; and

Figs. 5, 6, and 7 are perspective views of modified forms of adapters embodying the invention.

Referring now to the drawing, the brush holder assembly shown in Fig. 1 comprises an arm 10 to which is securely attached an insulated supporting pin 11 which is provided for clamping the assembly to the frame of a dynamoelectric machine. An insulated spacing collar or porcelain bushing 12 is provided at the lower end of the pin 11 to space the arm 10 from a bracket or clamp in which the pin 11 is secured. At the outer end of the arm 10 there is provided a brush guide 13 shown in section for holding the brushes in position for engagement with the rotor of the dynamoelectric machine. A two-piece brush 14 is mounted in the guide and downward pressure against the brush is exerted by a brush finger 15 attached in the usual manner to a coil spring 16 mounted on a pin 17 midway between the ends of the arm. A current shunt is provided between the finger 15 and a connector 19 on the arm 10 to minimize the passage of current through the spring 16. The flexible copper brush shunts or pigtails indicated at 20 which conduct current to the brushes 14 are secured to the arm 10 in the usual manner by screws 22. In the construction illustrated, the pressure of the brush finger 15 is exerted against the double brush 14 through a brush adapter or wear compensator 23 and presses the brush 14 against the commutator of the dynamoelectric machine diagrammatically indicated by the dotted circle 24. The two-piece brush 1'7 as illustrated in Fig. 1 has been worn to such an extent that the brush finger 15 can no longer follow the brush down and exert the proper pressure except for the presence of the adapter 23.

The construction and arrangement of the adapter 23 will be more readily apparent from Figs. 2 and 3 which illustrate the adapter in position on the tWo piece brush 14. The adapter comprises a block of suitable material which may be either electrically conducting or non-conducting and may, for example, be molded from metal or a suitable plastic material. It is desirable that the block 23 be of relatively light construction and when it is made of metal, aluminum is preferable for this reason. The block 23 is made of the same cross-sectional dimensions as the double brush 14 and the lower face of the block which engages the top of the brush is shaped to conformto the shape of the top of the brush which, as illustrated here, is convex upwardly. 'Itwill thus be seen that the downward pressure'on the block 23 and thence against the tops of the two halves of the brush 14 provides a lateral restraint which tendsto maintain the two parts of trated is of the type in which each half of the brush is provided 'with two pigtails'or brush shunts '20, oneon each side of the brush. Theadapter'block Z3 is provided l with recesses 26 extending in alignment with the direction of brush movement and encircling the pairs of leads 20, one from each brush half, at the two sides of the brush 14. The recesses or guideways 26 are open at the ends of the blocks 23 as indicated at 27. This allows the block easily to be slipped around the pairs of leads 20 whereupon it may be positioned on the brush 14. The leads from brushes such as the brush 14 illustrated are commonly all attached to a single terminal or eye indicated at 28 in Fig. l, and in view of the flexibility of the leads the adapter block 23 may readily be placed in position with the leads passing through the two recesses 26. When the adapter is in position as illustrated in Fig. 2, the. guide passages 26 cooperate with the brush shunts 20 to hold the two halves of the brush and the adapter in assembled relationship so that the entire assembly may be lifted from the brush guide 13 for inspection without displacing the adapter from the assembly. This greatly facilitates the handling of the brushes during inspection and the adapter block 23 is not easily dislodged in the inspection routine although it is easily removed or replaced when this is found necessary. The height of the block is made substantially equal to the normal amount of wear which is permissible during operation of the dynamoelectric machine brushes. It Will be noted that the normal range of movement of the brush finger is from a position substantially that shown in Fig. 1 to a lower position in which it engages the bottom of a recess 29 commonly provided to afford movement of the finger beyond the top of the brush guides 13. It is this range of movement which determines the normal height of the adapter block 23. When a brush is worn so that it would normally require replacement, the brush finger is removed and the brush drawn out whereupon a block 23 is inserted and the brush and block as a unitary assem' bly placed back in the guide 13. In this position as shown in Fig. 1, the length of the assembled brush and adapter is substantially that of a new brush, and the worn brush may then be permitted to wear substantially the same distance again thereby saving a large amount of brush material and making each brush usable for about double its normal life. The top of the block 23 is preferably shaped in a manner similar to the top of the brush 14 so that the bearing area of the finger 15 on top of the block is essentially the same as it would be on top of the brush 14. Thus the forces exerted and the characteristics of the operation of the combined brush and adapter assembly are essentially the same as those of the original full length brush. The width of the guide passages 26 is determined by the spacing of the shunts or leads the width of the passages being made the same as the distance between the outer sides of the pair of leads as clearly shown in Fig. 3. Thus the engagement of the sides of the passages 26 and the outer edges of the leads 20 together with the conformation of the block 23 to the form of a top of the brush 14 serve to hold the block and the brush in good working engagement. Furthermore, in the case of the two-part brushes such as those illustrated, the adapter block 23 acts as a tie holding the two parts of the brush together during their handling outside the brush guides; this facilitates handling of the brush and adapter as an assembly and minimizes ditficulties during servicing due to the separation of the two parts of the brush.

In Fig. 4, the invention has been shown in connection with a single piece block-type carbon brush 31 which is provided with an adapter block 32 similar to the block 23 of Figs. 1 and 2. The block 32 is provided with guide passages 33 which are fitted around shunts or leads 34, one at either side of the brush. The guide passages 33 are made so that they fit closely about the leads 34. and are provided with lateral openings 35 in the ends of the block 32 so that the block may readily be inserted in position in a manner similar to the block 23 of the'first modification. The block 32 is shaped to fit the top of the brush 31 and has a cross-sectional area the same as that of the brush 31 so that the brush and block may ride as a unit in the brush guide. The top of the block 32 is shaped to provide the same configuration as the top of the brush 31. The engagement of the guide openings 33 and the shunts 34 provides an arrangement for holding the block 32 in proper position on the brush 31 during handling and servicing and facilitates the servicing of the dynamoelectric machine.

In Fig. 5 there is illustrated an adapter block 37 having a single guide opening 38 near one end and an opening 39 which allows the block to be inserted over the shunt lead in a manner similar to that of the other modifications. The block 37 is of a form provided for brushes having a single shunt connector near one side and the opening 38 is shaped and has dimensions such that it provides an effective arrangement for holding the adapter block on the brush during handling and facilitates the guiding of a block into position over the brush in the brush guides during servicing.

The form of adapter block illustrated in Fig. 6 is similar to that shown in Fig. 5 and comprises a block 40 provided with a centrally located guide opening 41 opening into the front side of the brush as indicated at 42. This block, in the same manner as the other blocks illustrated, is shaped to conform to the shape of the top of the brush and is of a cross-section such that it may readily be positioned in the brush guide.

In Fig. 7 there is illustrated an adapter block 44 which is shaped in a manner similar to the block 23 of Fig. 2 but has guide openings 45 which extend laterally into opposite sides of the block 44. This type of block may readily be inserted in position on the brush by pushing it midway between the pair of brush shunts as the shunts 20 illustrated in Fig. 2 and then rotating it in position so that the shunts enter the openings 45. This form is found useful when the lengths of the brush shunts or their location in the machine make it difficult to insert a block in the form of the open ended block 23 in Fig. 2;

The compensating adapters made in accordance with this invention are extremely simple to install and to use and effectively increase the length of life of the brushes of dynamoeleetric machines. Furthermore, servicing time is decreased because instead of the replacement operation which requires removal of the shunts or brush leads, it is merely necessary to insert the adapter block without removing the leads from the brush holder assembly. Furthermore, the adapter blocks serve to hold the brush halves of two-part brushes in assembled relationand facilitate the inspection of the brushes and the initial insertion of the adapter. It will readily be understood that the-cross-sectional area and shape of the adapter blocks are not critical it being, of course, essential that the adapter block be of such size and shape that it rides in the brush guide; preferably the adapter blocks are made of the same cross-sectional shape and size as the brushes with which they are to be used and although they may be made smaller they will normally and preferably be of substantially the same size as the brush crosssection.

Although specific embodiments of the invention have been illustrated and described, various changes will occur to those skilled in the art and, therefore, it is not desired that the application be limited to the specific details illustrated and described and it is intended by the appended claims to cover all modifications which fall within the spirit and scope of the invention.

I claim:

1. A. wear compensating adapter for a dynamoelectric machine brush of the type having a conducting lead extending from onev end thereof comprising a block having a crosssectionof substantially the same size and shape as the brush and having a depth corresponding to the amount of normal permissible brush wear, said block having an open sided recess extending therethrough in alignment with the brush lead to accommodate the lead and afford seating of the block on the brush whereby said adapter may be inserted between the brush and a pressure finger to restore the finger to its normal working range and afford further wear of the brush, said recess having a depth substantially greater than the thickness of the lead to minimize accidental displacement of the block from the lead.

2. An adapter as set forth in claim 1 wherein the face of the adapter for engagement with the brush is shaped to "the configuration of the end of the brush.

3. A wear compensating adapter for a dynamoelectric machine brush of the type having two spaced conducting leads extending from one end thereof comprising a block having a cross section of substantially the same size and shape as that of the brush and having a depth corresponding to the amount of normal permissible brush wear, said block having open sided guide passageways therethrough in opposite faces thereof and in alignment with the brush lead positions and extending in the direction of the longitudinal axis of the brush for receiving the leads by lateral movement with respect thereto and for affording guiding of the block to and seating of the block on the top of the brush whereby the block may be inserted between a brush and a pressure finger to restore the normal working range of the finger.

4. A wear compensating adapter for a dynamoelectric machine brush of elongated substantially rectangular cross section having two spaced conducting leads extending from one end thereof and each adjacent a respective one of the shorter sides of the cross section of the brush, comprising a block having a cross section of substantially the same size and shape as that of the brush and having a depth corresponding to the amount of normal permissible brush wear, said block having guide passages therethrough in alignment with the brush lead positions, one of the guide passages opening laterally through one of the longer sides of said block and the other laterally through the other side thereof for aflording guiding of the block to and seating of the block on the top of the brush whereby the block may be inserted transversely between the leads of the brush and rotated so that the leads pass through the respective ones of said openings, said block when in position on a worn brush restoring the normal working range of the brush pressure finger.

5. A wear compensating adapter for a dynamoelectric machine brush of the type including a pair of separate brush members each having two spaced conducting leads extending from one end thereof, comprising a block having a cross section of substantially the same size and shape as that of the brush with which it is to be used and having a depth corresponding to the normal permissible wear of the brush, said block having two open sided guide passages one near each end in alignment with the brush lead positions, the width of each passage being substantially the distance between the opposite outer sides of the leads of each pair of leads of the brush, the side openings of said passages being restricted and extending outwardly through the ends of said block, the bottom of said block being shaped to conform to the shape of the top of the brush, whereby said block may be placed on the end of a brush and the pairs of leads introduced through the side openings into said passages in engagement with the walls thereof and said block may be seated on the top of the brush and retain the two members of the brush in assembled relationship.

6. A wear compensating adapter for a dynamoelectric machine brush of the type having two spaced conducting leads extending from one end thereof comprising a block having a cross section of substantially the same size and shape as that of the brush with which it is to be used and having a depth corresponding to the normal permissible wear of the brush, said block having an open sided guide passage in alignment with the brush lead position, the width of the passage being substantially the distance between the outer sides of the leads of the pair of leads of the brush, the said openings of said passages being restricted and extending outwardly through the block, the bottom of the block being shaped to conform to the shape of the top of the brush whereby said block may be placed on the end of a brush and the pair of leads introduced through the side opening into said passage and into engagement with opposite walls thereof and be retained in position by the engagement of said passage and the brush leads.

References Cited in the file of this patent UNITED STATES PATENTS 1,835,513 Munday Dec. 8, 1931 FOREIGN PATENTS 63,191 Sweden June 21, 1927 297,959 Switzerland June 16, 1954 521,453 France Mar. 5, 1921 

